TRENTON, N.J. — Gov. Chris Christie fired one of his top aides Thursday and apologized over and over for his staff's "stupid" behavior, insisting during a nearly two-hour news conference that he had no idea anyone around him had engineered traffic jams as part of a political vendetta against a Democratic mayor.

"I am embarrassed and humiliated by the conduct of some of the people on my team," he said as he addressed the widening scandal that could cast a shadow over his expected run for the White House in 2016.

Christie, who had previously assured the public that his staff had nothing to do with the lane closings in September that caused major backups at the George Washington Bridge, said he fired Deputy Chief of Staff Bridget Anne Kelly "because she lied to me" when he demanded weeks ago that anyone who knew anything about the episode come forward.

New Jersey Gov. Chris Christie. (Mel Evans, The Associated Press)

The gridlock in Fort Lee delayed emergency vehicles, school buses and countless commuters for four days.

Kelly was the latest casualty in the scandal. Two other top Christie appointees have resigned in the past few weeks.

The investigation broke wide open Wednesday, with the release of e-mails and text messages that suggested Kelly arranged the traffic jams to punish Fort Lee's mayor for not endorsing Christie for re-election.

In other developments:

• The chief federal prosecutor in New Jersey, U.S. Attorney Paul Fishman, said he is "reviewing the matter to determine whether a federal law was implicated."

• David Wildstein, a Christie appointee who resigned from the Port Authority of New York and New Jersey after being implicated in the scandal, was found in contempt Thursday by a legislative committee after he invoked his Fifth Amendment right against self-incrimination and refused to answer questions. The Port Authority operates the bridge.

• Christie later traveled to Fort Lee and apologized in person to Mayor Mark Sokolich.

Members of New Jersey Gov. Chris Christie's staff listen to his news conference Thursday in Trenton. (Mel Evans, The Associated Press)

The governor brushed off questions about the effect on his presidential prospects, saying he was too busy governing the state to think about that. "I am absolutely nowhere near beginning that consideration process," he said.

Some political analysts on both sides of the aisle said Christie would probably pull through all right — provided there are no more surprises.

Besides firing Kelly, Christie cut ties to former campaign manager Bill Stepien, asking him to withdraw a bid to become the next state GOP chairman. The governor said he was disturbed by the "callous indifference" displayed by Stepien in the e-mails released Wednesday.

Kelly hasn't commented. Christie said he hadn't spoken to her or asked to hear her side of the story since the e-mails were released, saying he didn't want to be accused of trying to influence a possible witness.

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